The ISPNPP monitors neutron levels in the wrecked Unit Four building, which still contains a molten slurry of uranium fuel rods, zirconium cladding, graphite control rods, and melted sand. As uranium fuel nuclei split apart, they release neutrons that strike other uranium atoms, causing them to split as well.
Meltdowns such as the one at Chernobyl, and more recently at Japan’s Fukushima, are the result of a runaway chain reaction. As it turns out, keeping it dry might be even worse. Ever since the meltdown and initial cleanup, engineers have worried that rainwater leaking into the building could cause another nuclear event. The organization began construction of the enormous arch-shaped NSC in 2010 (see above) with the aim of keeping the existing remains of the reactor stable for eventual dismantling, and also to keep the site dry. Ukraine’s Safety Problems of Nuclear Power Plants (ISPNPP) is currently responsible for securing Chernobyl.